Method of constructing foundation substructure and a building

ABSTRACT

The present invention provides a method of constructing a foundation substructure and a building involving pouring concrete between resilient sheets of insulating material, preferably polystyrene, so as to form a complete concrete shell.

FIELD OF THE INVENTION

The present invention relates to a method of constructing a foundationsubstructure and a building.

BACKGROUND OF THE INVENTION

Formworks are structures of boards that make up forms for pouringconcrete in construction. To date, a self-supporting permanent formworkstructure that can be put up by manhandling alone and has excellentinsulation has not been produced. Furthermore, a structure that whenused results in good acoustic performance, high thermal capacity,strength and resilience has not been produced.

SUMMARY OF THE INVENTION

The present invention seeks to address these issues.

According to one aspect of the present invention there is provided amethod of constructing a building, comprising the steps of:

-   -   a) erecting a plurality of panels to define the walls;    -   b) installing a support rail at the height of a floor or roof;    -   c) attaching at least one sheet of material to the support rail        so as to define a floor or roof    -   d) pouring concrete between the panels of insulating material        and over the at least one sheet of material so as to form the        walls and floor or roof of the building

Preferably said panels are formed of two sheets of synthetic insulatingmaterial held in spaced relation to each other by a plurality ofspacers.

Preferably said support rail is made of lightweight cold rolled steel.

Preferably said sheets of material are sheets of corrugated steel.

Preferably said spacers are made of aerated concrete.

According to another aspect of the present invention there is provided abuilding wherein at least part of one wall comprises two sheets ofinsulating material between which is a layer of concrete.

Preferably said insulating material is extruded polystyrene.

Preferably all of the external walls of said building comprise twosheets of insulating material between which is a layer of concrete.

Preferably the building comprises a first floor or roof made ofconcrete, and the concrete of said first floor or roof is directlybonded to the concrete of said walls.

Preferably the building comprises a concrete foundation slab, and theconcrete of said foundation slab is directly bonded to the concrete ofsaid walls.

According to a further aspect of the present invention there is provideda method of constructing a foundation substructure comprising the stepsof:

-   -   a) laying a concrete foundation;    -   b) securely fixing outside perimeter members to said foundation        to define the outside perimeter of a wall;    -   c) positioning foundation blocks comprising an outside perimeter        sheet and an inside perimeter sheet held in spaced relation to        each other against said outside perimeter members, wherein the        outside perimeter sheet is taller than the inside perimeter        sheet;    -   d) securely fixing inside perimeter members against the inside        perimeter of said foundation blocks;    -   e) filling said foundation block with concrete to the height of        the inside perimeter sheet;    -   f) building the inside foundation structure up with hardcore;    -   g) overlaying the hardcore with an insulating sheet such that        the top of the insulating sheet is level with the height of the        inside perimeter sheet; and    -   h) pouring a concrete floor slab over said insulating sheet to        the height of external perimeter sheet.

Preferably said outer perimeter members and said inner perimeter membersare softwood battens.

Preferably said outside perimeter sheet, said inside perimeter sheet andsaid insulating sheet are made of extruded polystyrene.

According to yet a further aspect of the present invention there is aprovided a foundation substructure comprising at least one foundationwall comprising two sheets of resilient material between which is alayer of concrete.

Preferably said foundation wall is adjacent to a further sheet ofinsulating material and part of the upper surface of said foundationwall and said further sheet of insulating material support a slab ofconcrete.

Preferably said sheets of insulating material are extruded polystyrene.

Preferably said further sheet of resilient material is extrudedpolystyrene.

BRIEF DESCRIPTION OF THE DRAWINGS

A specific embodiment will now be described with reference to theaccompanying drawings, of which:

FIGS. 1 to 8 show the method of building construction excluding thefinal step of pouring concrete;

FIG. 9 shows a vertical cross-section of a wall of a building beingconstructed according to the method of FIGS. 1 to 8 resting on afoundation substructure;

FIG. 10 shows a vertical cross-section through a wall and floor of abuilding being constructed according to the method of FIGS. 1 to 8;

FIG. 11 shows a horizontal cross-section through two walls of a buildingbeing constructed according to the method of FIGS. 1 to 8;

FIG. 12 shows a schematic vertical cross-section through a panelaccording to the present invention; and

FIG. 13 shows a vertical cross section through the base of a columnerected according to the method of FIGS. 1 to 8.

DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS

Before the building is constructed, a foundation substructure for thebuilding is laid. As shown in FIG. 9, the foundation substructure has asits base a concrete foundation 1, which should be as level as possible(±5 mm). Softwood battens 2 are attached to the foundation around theoutside perimeter of the walls using shot-fired fixings or rawlbolts at300 mm centres. Foundation blocks comprising extruded polystyrene sheets4,5 are positioned against battens 2, these sheets 4,5 being heldtogether in spaced relation by spacers (not shown in the diagram).Preferably the spacers are 103*103 mm blocks of aerated concrete with acrushing strength of 7 N/mm², and fixed in position in the foundationblocks using A9267 adhesive, as sold by Strathbond Ltd. The foundationblocks are preferably ‘Formworks F1’™ foundation blocks. Externalperimeter sheet 4 is higher than internal perimeter sheet 5. Softwoodbattens are secured onto the foundation 1 around the inside perimeter ofthe walls using shot-fired fixings or rawlbolts at 450 mm centres.Preferably 50*75 mm softwood battens are used for both 2 and 7.

The foundation blocks are then filled to the underside of floor slablevel to form foundation walls, i.e. to the full height of panel 5 usingwell compacted concrete, as specified by the Engineer, usually 30 kN/m²,slump 75 mm±25 mm, maximum aggregate size 10 mm. It is important thatthe concrete slump is within the limits specified as too high a slumpcan increase formwork pressures and can lead to deformation and possiblebursting. Concrete may by poured using a pump, skip or other methods,with care taken that the concrete is not placed into the formwork tooquickly. The pump should have a maximum hose diameter of 75 mm,preferably with a swan-neck to reduce the velocity of the concrete.Concrete should be lightly compacted as the pour proceeds, the mostsuitable methods being gentle rodding with a length of reinforcing barand tapping the outside of the formwork. The foundation walls should bechecked to ensure they remain straight and plumb as they are filled andchecked again when the fill is complete. Excess concrete is cleaned fromthe tops and surfaces of the foundation walls before it has ‘gone off’.

Hardcore 3 is placed on the side of sheet 5 which will be the inside ofthe building. Insulating polystyrene sheet 6 is laid over hardcore 7.DPM (acronym: Damp Proof Membrane) is then laid over insulatingpolystyrene block 6 and concrete floor slab 8 is poured to the height ofexternal perimeter sheet 4. Once the concrete has set, the substructureis complete.

This insulated substructure avoids labour below ground and the excessiveuse of concrete that is inherent with strip and trench fill foundationsrespectively.

Once the substructure has been completed, construction of the buildingitself may be commenced, though the building may of course also be builton any other suitable foundations.

A base channel 9 is secured along the path that the walls are to beerected on, in the present embodiment around the perimeter of theconcrete floor slab 8 using M10 rawlbolts at 450 mm centres. In thepresent embodiment the channel is a 75*130*3 mm C-section, however it ispreferable to use two angles such that in the middle of the channel theconcrete slab 8 is exposed. This means that when the concrete wall ofthe building is later poured, the building wall will form an airtightconcrete-to-concrete seal with slab 8.

Turning to FIG. 2, once the channel has been secured, columns 10 areattached to the channel with two Teks™ self-drilling, self-tappingscrews 11 on each side as seen in FIGS. 9 and 13. Corner columns 10 aare similarly attached to the channel. The columns are made oflightweight cold rolled C section steel bolted back to back. There areholes punched in the columns to allow concrete to flow through and bond.The corner columns 10 a also incorporate a square section joining piece.

As seen in FIG. 3, panels 13 are placed between the columns and the edgeof the panels are fixed to the columns using 110 mm long ExFix™fasteners at 300 mm vertical centres 12, as seen in FIGS. 9 and 11.Alternative fixings may of course be used. For example plastic tubularwashers held in place by a self-tapping screw wherein the tube has a‘mushroom’ head and the screw fits inside the tube. Such fixings havethe advantage that they minimise heat transfer from the inside to theoutside as the screw is screw is buried in insulation. This improves thethermal performance of the wall.

Panels 13 are preferably ‘Formworks F1’™ panels. Panels 13 comprise twosheets (13 a, 13 b) of extruded polystyrene held together in spacedrelation by spacers 14 at approximately 500 mm centres. FIG. 12 is aschematic cross section through a panel showing spacers 14. Spacers 14are 103*103 mm blocks of aerated concrete with a crushing strength of 7N/mm², and fixed in position in the panels using A9267 adhesive, as soldby Strathbond Ltd. The size of the panels may vary from 600 mm*2500 mmup to 1200 mm*2500 mm. Typically the sheets are 80 mm thick. Typicallythe space between the sheets is 140 mm. As can be seen from FIG. 3,sheet 13 a on the outside of the wall is taller than sheet 13 b on theinside of the wall. The panels are prefabricated off-site, where serviceducts, windows, doors etc. may be incorporated into the panels underfactory conditions.

It is evident that the use of columns separate to the panels is notessential and self-supporting panels with, for example, columnsincorporated may be used.

Turning to FIG. 4, once the panels are in place, the floor support rail15 is attached to the columns around the inner perimeter of the walladjacent to the top of sheet 13 b using four Teks™ self-drilling,self-tapping screws 16 into each column. The support rail is a 127*63 mmC-section.

As can be seen in FIG. 5, cill, head and minor infill panels 17 are thenattached onto the columns using 110 mm long ExFix™ fasteners at 300 mmcentres. Any reinforcement that may be required above the openings inthe walls is introduced at this stage. The sections of column adjacentto doors, windows etc. are blocked with appropriate pieces of timber toprevent concrete spilling out through the holes.

Turning to FIG. 6, corrugated steel sheeting 19 is positioned on thesupport rail and a check is made to ensure that the corners are rightangles. The sheeting has a W-section. The sheeting is secured to supportrail 15 using Teks™ self-drilling, self-tapping screws 18 at 300 mmcentres. Further corrugated steel sheeting 19 is then used positionedand similarly secured to the support rail so as to create the formworkfor a floor or roof. The floor is propped up using Acro™ props or anysimilar means below temporary beams.

The steel frame thus constructed provides both temporary support to theformwork, ensuring that it is stable until the pour is complete, and itreplaces reinforcing steel, which is complex and expensive to fix. Thecolumns are specially designed to create a composite structure with theconcrete. The permanent steel floor formwork holds the structure squareand rigid until the concrete is poured. The structure isself-supporting. This dual function of the steel frame makes the systemefficient and cost effective.

As can be seen in FIG. 8, a safety rail 20 is secured to columns for usewhen pouring the concrete. Any necessary reinforcement required for thewalls such as starter bars, are fixed in accordance with the Engineersspecifications.

The concrete may then be poured into the wall formwork. This is done inwell compacted layers not exceeding 900 mm in depth. The concretestrength is specified by the Engineer, usually 30 kN/m2, with slump 75mm±25 mm and maximum aggregate size 10 mm. Again, it is important thatthe concrete slump is within the limits specified as too high a slumpcan increase formwork pressures and can lead to deformation and possiblebursting. Fibre can be added to the mix both to increase tensilestrength of the concrete and to provide shrinkage crack resistance. Theconcrete may be poured using a pump, skip or any other suitable means,taking precautions that the concrete is not placed into the formwork tooquickly. Pumps should have a maximum hose diameter of 75 mm, preferablywith a swan-neck to reduce the velocity of the concrete. The concreteshould be lightly compacted as the pour proceeds, the most suitablemethods being gentle rodding with a length of reinforcing bar andtapping the outside of the formwork. The walls should be checked toensure that they remain straight and plumb as they are filled andchecked again when the fill is complete.

Any reinforcement required for the floor in accordance with theengineers specifications should then be positioned and secured. Suchreinforcement may be a mesh 21. The concrete slab 22 is then poured ontothe corrugated steel sheeting 19, and brought to the level of the top ofsheet 13 a.

Once the concrete has reached the required strength, this procedure maybe repeated to construct upper floors. To begin repeating the procedurecolumn extensions are bolted onto the existing columns, and the safetyrail 20 is removed and stored for later use. Galvanised steel angles(23, 24) are used to locate the base of the upper panels, one of theangles 23, a 75*75*3 mm angle being attached to the concrete slab 22 andthe other two angles 24, being 75*50*3 mm angle attached to the columns.All of the angles are attached using Teks™ self-drilling, self-tappingscrews. 110 mm long ExFix™ fixings 25 are used to secure the top andbase of each panel to the angles at 300 mm horizontal centres. When itis necessary to join two lengths of column, splice plates should befixed in accordance with the Engineers instructions.

A finish 26 may later be applied. Finishes range from elastomeric paintsthrough modified thin coat renders, acrylic brick and stone slips totimber cladding and more sophisticated rain screen systems.

The method as described has many advantages. The insulating panels areleft in place after they have been used as formwork thus providinginsulation. Conventional formwork has to be removed, transported, andstored or disposed of, a wasteful and expensive process. The insulationprovides thermal performance and protection for the concrete throughoutits life. Expanded polystyrene may be used in place of extrudedpolystyrene; indeed, any suitable material may be used.

The floors and roofs are cast on corrugated steel formwork, and togetherwith the walls provide a strong airtight shell.

This concrete shell provides structural strength and durability. Unlikepre-cast panel or timber frame systems, airtight integrity isautomatically achieved and maintained for the life of the building. Thisallows for efficient ventilation with heat recovery. The inherentstrength of the concrete shell creates a secure building resistant tofire, extreme weather and physical attack.

The concrete shell provides thermal capacity, resulting in lower energyuse and a healthier environment. The savings in energy during thebuildings life due to thermal capacity contribute significantly to lowerrunning costs and sustainability. Typical wall panels have 80 mm ofinsulation on each side of a 140 mm cavity and together with finishesachieves a U value of 0.17 w/m²/K. This can be increased by addingadditional insulation.

The concrete shell also provides acoustic mass; i.e. the building ishighly insulated from sound.

The above embodiment is by way of example only, many variations arepossible without departing from the scope of the invention.

1. A method of constructing a building, comprising the steps of: a)erecting a plurality of panels to define the walls; b) installing asupport rail at the height of a floor or roof; c) attaching at least onesheet of material to the support rail so as to define a floor or roof d)pouring concrete between the panels of insulating material and over theat least one sheet of material so as to form the walls and floor or roofof the building
 2. The method of claim 1 wherein said panels are formedof two sheets of synthetic insulating material held in spaced relationto each other by a plurality of spacers.
 3. The method of claim 1wherein said support rail is made of lightweight cold rolled steel. 4.The method of claim 1 wherein said sheets of material are sheets ofcorrugated steel.
 5. The method of claim 2 wherein said spacers are madeof aerated concrete.
 6. A building wherein at least part of one wallcomprises two sheets of insulating material between which is a layer ofconcrete.
 7. The building of claim 7 wherein said insulating material ispolystyrene.
 8. The building of claim 7 wherein all of the externalwalls of said building comprise two sheets of insulating materialbetween which is a layer of concrete.
 9. The building of any of claim 7further comprising a first floor or roof made of concrete, and theconcrete of said first floor or roof is directly bonded to the concreteof said walls.
 10. The building of claim 7 further comprising a concretefoundation slab, and the concrete of said foundation slab is directlybonded to the concrete of said walls.
 11. A method of constructing afoundation substructure comprising the steps of: a) laying a concretefoundation; b) securely fixing outside perimeter members to saidfoundation to define the outside perimeter of a wall; c) positioningfoundation blocks comprising an outside perimeter sheet and an insideperimeter sheet held in spaced relation to each other against saidoutside perimeter members, wherein the outside perimeter sheet is tallerthan the inside perimeter sheet; d) securely fixing inside perimetermembers against the inside perimeter of said foundation blocks; e)filling said foundation block with concrete to the height of the insideperimeter sheet; f) building the inside foundation structure up withhardcore; g) overlaying the hardcore with an insulating sheet such thatthe top of the insulating sheet is level with the height of the insideperimeter sheet; and h) pouring a concrete floor slab over saidinsulating sheet to the height of external perimeter sheet.
 12. Themethod of claim 12 wherein said outer perimeter members and said innerperimeter members are softwood battens.
 13. The method of claim 12wherein said outside perimeter sheet, said inside perimeter sheet andsaid insulating sheet are made of polystyrene.
 14. A foundationsubstructure comprising at least one foundation wall comprising twosheets of material between which is a layer of concrete.
 15. Thefoundation substructure of claim 15 wherein said foundation wall isadjacent to a further sheet of insulating material and part of the uppersurface of said foundation wall and said further sheet of insulatingmaterial support a slab of concrete.
 16. The foundation substructure ofclaim 15 wherein said sheets of insulating material are polystyrene. 17.The foundation substructure of claim 15 wherein said further sheet ofmaterial is polystyrene.